Triggering a thyristor / thyristor bridge

[Jim Edwards]

Can anyone help me with the following circuit.
I am replacing a bridge rectifier in a dc welding set. I have acquired 2 thyristor / thyristor modules (International Rectifiers IRKT 250 / 16). I am wanting to build a circuit to trigger the thyristors. I dont need any phase control, I want them to be fully on all the time. I would like to isolate the control from the power side using trigger transformers. The bridge supply will be 20 to 30 v AC. Would I be better supplying the control voltage through a seperate transformer to synchronise to the mains?
Can anyone design me a circuit that takes into account the cost of the modules. I would hate to blow them by miss firing them.
Thanks in anticipation of a reply.

 

[Hero999]

You could use an opto TRIAC such as the MOC3041. The circuit is on the datasheet.

https://www.electro-tech-online.com/custompdfs/2010/05/moc3041.pdf

 

[tcmtech]

If you are just intending to use them as big diodes then all you need to do is tie the gate lead of each SCR to its own anode through a 20 - 100 ohm resistor. They will be self triggering and will work just like regular diodes that way.

 

[Jim Edwards]

Hi tcmtech
Thanks for the quick response. I didnt think it was as simply as that. You are correct, I just want to use them as big diodes.
Hopefully I will be back welding again soon.
Thanks again.

Regards
Jim Edwards